In order to provide antifouling properties, photocatalytic coating materials including photocatalytic substances such as titanium oxide are generally applied to window glass, lens, inner and outer wall surfaces of buildings, various rooftops, advertising signboards, and solar battery panels, which are intended to face outdoors or for outdoor use; and charging surfaces, condensation surfaces, and icing surfaces, which are intended to face indoors or for indoor use. Photocatalytic substances subjected to excitation light accelerate various chemical reactions, which leads to exertion of antifouling properties. Such antifouling properties exerted by photocatalysts are due to hydrophilic properties of surfaces of the photocatalysts and oxidative degradation of organic substances adhered on the surfaces.
However, such conventional coating materials including photocatalysts may cause oxidative degradation of surfaces of some articles on which the coating materials applied. Therefore, coating materials which provide high hydrophilic coating films without using photocatalysts have been needed.
Patent Document 1 discloses, as a photocatalyst-free coating material for outer walls of structures, a specific composition of a hydrophilic coating material composed only of Nafion (registered trademark of EI du Pont de Nemours and Company), which is a fluororesin.
Patent Document 1: JP 2006-45370 A